1. Field of the Invention
This invention relates to a lightweight getter for contaminants, particularly an aerogel mesh getter therefor.
2. The Prior Art
Optical sensors in space-based astronomical observatories and other observation satellites are often required to detect low-radiance objects against relatively bright backgrounds such as the Earth and the sun. This requires that the optical system have a high out-of-field-of-view rejection capability and thus low scatter optical surfaces (mirrors and lenses). Launch, deployment and satellite operations such as gimbal motions create vibration-induced contaminants which have a high probability of becoming attached to optical surfaces or accumulating in the sensor's field of view. Propulsion effluents, nonmetallic material outgasing and the natural space environment also produce contaminants that can deposit onto surfaces sensitive thereto such as lenses, mirrors and solar collectors.
To alleviate the above surface contamination problem, certain devices have been developed which direct a spray, jet or beam at a surface to dislodge the contaminant particles therefrom. This is, e.g. a gas-sold snow mixture spray or ion beams are applied to remove contaminants from the optical surfaces. However, one removed from such surface, these species must be collected to prevent their re-deposition on an optical surface and/or their floating in the field of view of an optical instrument.
In the prior art, collectors known as "getters" have been employed for the purpose of collection or capture of the above contaminants. These prior art getters have taken the form of one or more layers of metal mesh, charged plates and charged dielectric plates (electrets). However the metal mesh device, e.g., of aluminum alloy, are brittle and have desorption rates and ablation tendencies. The charged plates require kilovolts of charge which is unacceptable for a satellite due to, e.g. arcing problems in space. The charged dielectric plates have capture radii too low to be useful in practice.
Further, high performance optical and micro electronic components have ever tightening contamination specifications placed upon them. Contamination is now seen as a major reason for the degradation of space based optical systems and failure of high density integrated circuits used through industrial and military systems. Contamination is currently controlled by the use of cleanrooms, process monitors and manual cleaning techniques which include solvent wipes, strippable coatings, wet-dry processes, ultrasonics and air purges. The major disadvantages of these techniques are their inability to remove submicron particles and the potential of leaving molecular residues on the cleaned surfaces. Some of these cleaning techniques can be damaging to delicate surfaces and/or have toxic waste products; for, e.g. biomedical applications such as virology research laboratories.
To address the above contaminant problem, certain contamination removal and collection techniques have been attempted in the prior art. However, some of these removal techniques create a flux of removed contaminates which can then re-deposit on clean surfaces or be ejected into the environment. Current collection devices, such as filters, charged metal plates and screens and charged dielectrics have collection efficiencies and capture radii incommensurate with the new nano-scale semiconductor devices, optical systems and biomedical cleanliness requirements.
Accordingly, there is a need and market for a contaminant getter that is effective and otherwise obviates the above prior art shortcomings.
There has now been discovered a lightweight contaminant getter that collects and holds particulate and molecular contaminants without the above-noted high voltage and ablation problems.